Method and apparatus for storing mobile station physical measurements and mac performance statistics in a management information base of an access point

ABSTRACT

A method and apparatus may be used for exchanging measurements in wireless communications. The apparatus may receive a request. The request may be a measurement request, and may include a request for a measurement of a parameter. The apparatus may transmit a report. The report may be a measurement report, and may include the requested measurement of a parameter. The apparatus may store the requested measurement of the parameter in a management information base (MIB).

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/183,549 filed on Jul. 18, 2005, which is a continuation of U.S.patent application Ser. No. 10/890,790 filed on Jul. 14, 2004 thatissued as U.S. Pat. No. 6,958,982 on Oct. 25, 2005, which claimspriority from U.S. Provisional Application No. 60/487,653 filed on Jul.16, 2003, which are all hereby incorporated by reference.

FIELD OF INVENTION

The present invention is related to wireless communication systems. Moreparticularly, the present invention is related to a method and systemfor transferring transmit power control (TPC) information between awireless transmit/receive unit (WTRU) and an access point (AP).

BACKGROUND

Wireless local area networks (WLANs) have become more popular because oftheir convenience and flexibility. As new applications for such networksare being developed, their popularity is expected to significantlyincrease.

Institute of Electrical and Electronics Engineers (IEEE) working groupshave defined an IEEE 802.11 baseline standard having extensions whichare intended to provide higher data rates and other networkcapabilities. Under the IEEE 802.11 standards, network entities includea management information base (MIB). The MIB may be either a mediaaccess control (MAC) layer MIB or a physical (PHY) layer MIB. Dataentries in a MIB table use IEEE 802.11 standards.

Network management entities (NMEs), connected to a WLAN, communicatewith each other by sending frames. There are three types of MAC framesdefined by the 802.11 standards: 1) data frames; 2) control frames; and3) management frames. There are also sub-types for each of these frames.For example, an action frame is a sub-type of a management frame. Actionframes are further defined by categories. Currently, action framecategories are defined as follows: 0—spectrum management; 1—quality ofservice management; 2—direct link protocol; and 3—radio measurement.

A service primitive is an internal signaling message used forinter-layer or inter-protocol entity exchanges, such as between astation management entity (SME) and a MAC layer management entity(MLME), with standardized message contents. Although a particular formatof message is not specified by the standards, the standards do specifythe content. Service primitives are typically used to initiate, confirmor report a particular action, such as by sending a particular frame formanagement purposes from one WTRU to another WTRU.

In accordance with IEEE 802.11 standards, an SME is incorporated intothe WTRU in order to provide correct MAC operation. The SME is alayer-independent entity that may be viewed as residing in a separatemanagement plane or as residing “off to the side.” Thus, the SME may beviewed as being responsible for such functions as the gathering oflayer-dependent status from the various layer management entities, andsimilarly setting the value of layer-specific parameters. The SMEtypically performs such functions on behalf of general system managemententities and implements standard management protocols.

Furthermore, according to IEEE 802.11 standards, a WTRU containsconfiguration settings in the MIB that control its behavior. It isimportant for an AP to be able to understand the configuration of eachWTRU in order to interpret the WTRU's behavior and to improveperformance in the context of WLAN radio resource management (RRM). Forexample, a WTRU keeps track, in its MIB, of successfully received butnot decodable data frames. This is important information for an AP toprovide a minimum level of quality of service to the WTRU.

RRM is one of the most important aspects in WLAN management. A WLAN canachieve significant performance enhancement by performing RRM, includingin-band interference mitigation and frequency re-use. For efficient RRM,it is necessary for an NME to retrieve WTRU specific TPC relatedinformation. A problem with the MIB data structure used in conventionalwireless systems is that TPC information of a WTRU is not stored in theMIB of an AP.

Interference mitigation is a classic technique used in wirelesscommunication systems to avoid interfering with other users in thevicinity by minimizing the amount of transmission power. The IEEE802.11h standard defines messaging of a maximum allowable transmit powerby means of BEACON and PROBE RESPONSE frames, and messaging by means ofTPC REQUEST and TPC REPORT frames to get the instantaneous transmitpower and link margin. An AP broadcasts a BEACON frame, or replies witha PROBE RESPONSE frame. A BEACON frame contains a country field, a powerconstraint field, a transmit power field, and a link margin field. Thecountry field contains the maximum regulatory power level. The powerconstraint field contains an offset value compared to the maximumregulatory power level. The transmit power field indicates the transmitpower used to transmit the TPC REPORT frame. The link margin field isset to zero in the BEACON and PROBE RESPONSE frames.

The request/report messaging and retrieving of a WTRU's physicalmeasurement data or MAC performance statistics, such as transmit/receive power levels and link margins in a basic service set (BSS), arekey parameters for supporting interference mitigation and RRM. However,these physical measurements or MAC performance statistics are not passedfrom an L1PHY or L2 MAC protocol entity to the SME, which serves as aninterface to an external WLAN RRM entity. The SME typically containsinterface software to read/write into the MIBs. For example, uponreceiving a command from a simple network management protocol (SNMP), aread of a particular MIB entry is reported back to the SNMP.

Currently, WLANs usually transmit at a much higher power level thanneeded. With TPC, the transmit power can be adjusted to the minimumlevel to still guarantee satisfactory signal reception while notcreating more interference than needed interference to other WTRUs. Itis also possible to perform effective load control and BSS rangeadjustments. Range adjustments, load balancing, and a maximum cellradius are determined by the transmit power of the AP and the receiversensitivity of the WTRU. If transmit power is not properly controlled,WTRUs at the edge of the cell lose connection to the AP and will beforced to re-associate to neighboring APs. Therefore, proper powercontrol enables effective load control and range adjustments.

SUMMARY

A method and apparatus may be used for exchanging measurements inwireless communications. The apparatus may receive a request. Therequest may be a measurement request, and may include a request for ameasurement of a parameter. The apparatus may transmit a report. Thereport may be a measurement report, and may include the requestedmeasurement of a parameter. The apparatus may store the requestedmeasurement of the parameter in a management information base (MIB).

The present invention is a method and wireless communication system fortransferring TPC information between a WTRU and an AP. The AP includes afirst management entity and a second management entity. The WTRUincluding a third management entity. The first management entity in theAP determines whether or not to adapt the transmit power level of theWTRU. The first management entity transmits a first message requestingTPC information to the second management entity in the AP if the firstmanagement entity determines to adapt the transmit power level of theWTRU. The second management entity may transmit a message to the firstmanagement entity confirming receipt of the first message.

The second management entity in the AP transmits a second message to theWTRU requesting that the WTRU provide TPC information to the AP. Inresponse to the WTRU receiving the second message, the third managemententity in the WTRU performs one or more physical measurements todetermine one or more TPC parameters. The third management entity thentransmits a third message including the requested TPC informationassociated with results of the physical measurements to the AP.

The measurements performed by the third management entity may include aWTRU transmit power level measurement, a link margin measurement, aclear channel assessment (CCA), a perceived signal-to-noise indication(PSNI) measurement, a received signal strength indication (RSSI)measurement, and a received channel power indication (RCPI) measurement.The first management entity may be an SME and the second and thirdmanagement entities may be MLMEs. The wireless communication system maybe a WLAN.

BRIEF DESCRIPTION OF THE DRAWING(S)

A more detailed understanding of the invention may be had from thefollowing description of a preferred example, given by way of exampleand to be understood in conjunction with the accompanying drawingwherein:

FIG. 1A is a block diagram of a wireless communication system operatingin accordance with the present invention;

FIG. 1B is a detailed block diagram illustrating the configuration of anAP and WTRU used in the wireless communication system of FIG. 1A;

FIG. 2 is a signal flow diagram showing communication between a WTRU andan AP for obtaining TPC information in accordance with the presentinvention;

FIG. 3 is a signal flow diagram showing communication between a WTRU andan AP for requesting and receiving a measurement report in accordancewith the present invention;

FIG. 4 is a signal flow diagram illustrating an exemplary process fortransferring TPC information using service primitives between networkmanagement entities in accordance with the present invention; and

FIG. 5 is a flowchart of an exemplary process including method steps fortransferring TPC information between network entities in accordance withthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Hereafter, a WTRU includes but is not limited to a user equipment, amobile station, a fixed or mobile subscriber unit, a pager, or any othertype of device capable of operating in a wireless environment. Whenreferred to hereafter, an AP includes but is not limited to a basestation, a Node-B, a site controller, or any other type of interfacingdevice in a wireless environment.

The present invention will be described with reference to the drawingfigures wherein like numerals represent like elements throughout. Thepresent invention applies as add-on to the WLAN IEEE 802.11 standards(802.11 baseline, 802.11a, 802.11b, and 802.11g), and also applies toIEEE 802.11e, 802.11h and 802.16.

The present invention may be further applicable to Time Division Duplex(TDD), Frequency Division Duplex (FDD), and Time Division SynchronousCDMA (TDSCDMA), as applied to a Universal Mobile TelecommunicationsSystem (UMTS), CDMA 2000 and CDMA in general, but is envisaged to beapplicable to other wireless systems as well.

The features of the present invention may be incorporated into anintegrated circuit (IC) or be configured in a circuit comprising amultitude of interconnecting components.

FIG. 1A is a block diagram of a wireless communication system 100including a plurality of WTRUs 105, a plurality of APs 110, adistribution system (DS) 115, an NME 120 and a network 125. The WTRUs105 and APs 110 form respective base service sets (BSSs) 130. The BSSs130 and the DS 115 form an extended service set (ESS). The APs 110 areconnected to the NME 120 through the network 125. The wirelesscommunication system 100 may be a WLAN.

FIG. 1B is a detailed block diagram illustrating the configuration ofthe APs 110 and WTRUs 105 used in the wireless communication system 100.The AP 110 includes a first management entity 150, a second managemententity 155 and a first MIB 160. The WTRU 105 includes a third managemententity 165, a fourth management entity 170 and a second MIB 175. TheMIBs 160 and 175 consist of one or more storage devices (e.g., acounter, a register or other memory device) used to store configurationparameters, performance metrics and fault indicators.

The first management entity 150 may be an SME. The second managemententity 155 may be an MLME. The third management entity 165 may be anMLME. The fourth management entity 170 may be an SME.

Referring to FIG. 1A, an RRM controller (not shown) residing in the NME120 communicates with the APs 110 via the network 125 and DS 115. TheAPs 110 wirelessly communicate with the WTRUs 105. The NME 120 sends amessage to the APs 110 to change admissible power levels in the AP's BSSby means of higher layer (layer 2 or higher) management protocols, suchas SNMP or Extensible Markup Language (XML). The NME 120 writesallowable maximum and minimum values into the MIB 160 of the AP 110.

A process is implemented in the AP 110 that regularly reads the entriesin the MIB 160 of the AP 110 and uses service primitives to send andreceive MAC signaling frames. The MAC signaling frames, such as BEACONor TPC REQUEST, MEASUREMENT REQUEST or the like, communicate to all ofthe WTRUs 105 in the cell.

When the AP 110 receives MAC signaling frames from the WTRUs 105 (e.g.,TPC REPORTS, MEASUREMENT REPORTS, or the like), the AP 110 takes thereported measurements and uses service primitives to write theperformance measurements in the MIB 160 of the AP 110. The NME 120 thenreads these MIB entries in the APs 110 via the management protocols tolearn the current system performance. The NME 120 controls the transmitpower level of the WTRUs 105.

The MIB may be either MAC MIB or PHY MIB. MAC MIB is generally preferredbecause most RRM units operate at the MAC level, which has a very fastresponse. Entries in the MIB table shall be included either in aper-WTRU table, which is preferred, or in a global statistics table. Bymaking these physical measurement data available to external entities bystoring them in the MIB of the AP 110, it is possible to keepinterference levels low, resulting in higher system capacity.

FIG. 2 illustrates a process which supports communication between a WTRU105 and an AP 110 in order to obtain TPC data in accordance with thepresent invention. Once an AP 110 decides to obtain TPC data from atarget WTRU 105, the AP 110 transmits a TPC request frame 205 to thetarget WTRU 105. In response to the TPC request frame 205, the WTRU 105performs one or more requested physical measurements and transmits a TPCreport frame 210 to the AP 110. The AP 110 then stores the TPC data inthe MIB 160 of the AP 110 which is made available to external entities,such as an NME 120.

Referring to FIGS. 1A and 1B, the process to obtain TPC data can also beinitiated by the NME 120, which in turn triggers the first managemententity 150 in the AP 110 to send a primitive to the second managemententity 155 to send a MAC signaling frame to the WTRU 105 and so on.

FIG. 3 illustrates a process which supports communication between a WTRU105 and an AP 110 in order for the AP 110 to request a WTRU 105 toperform one or more measurements and report specific physical parametersof the WTRU 105 to the AP 110. Once an AP 110 decides to requestphysical measurement data from a WTRU 105, the AP 110 transmits ameasurement request frame 305 to a target WTRU 105 for measuring andreporting certain physical parameters of the target WTRU 105. Themeasurements may include transmit power, link margin, a CCA report,received power indicator (RPI) histogram report, or any other physicalrelated measurements. These may be absolute values, statistical averagesor histogram values, or values that are calculated utilizing any type ofalgorithm or optimization routine. After performing the requestedmeasurement, the target WTRU 105 compiles measurement data and transmitsa measurement report frame 310 to the AP 110. The measurement data isstored in the MIB 160 of the AP 110 and, optionally, at the MIB 175 ofthe WTRU 105.

The MIB 175 in the WTRU 105 stores two different categories ofinformation. The first category includes a variety of physicalmeasurements such as signal power, interference levels, noisehistograms, or the like. The second category is a variety of MACperformance statistics such as CCA busy fractions, average back-offtimes, erroneous frame counters, or the like.

When the received physical measurement and MAC performance statisticsare stored in the MIB 160 of the AP 110, it is made available to anentity which is responsible for RRM. The MIB 160 may be either a MAC MIBor a PHY MIB. A MAC MIB is preferred because RRM messaging is alsoperformed in MAC layer, and it is much faster than PHY layer. Thesephysical measurement data are made available to external entities bystoring them in the MIB 160 of the AP 110. Thus, effective load controland BSS range adjustments become possible.

FIG. 4 is a signal flow diagram illustrating an exemplary process 400for obtaining TPC information using service primitives between an AP 110and a WTRU 105. Internal messaging is performed with service primitivesnewly introduced by the present invention. Using process 400, an AP 110may obtain TPC data from the WTRU 105 and store the TPC data in the MIB160 of the AP 110.

The AP 110 includes an SME 450 and an MLME 455. The WTRU 105 includes aMLME 465 and an SME 470. Referring to FIG. 4, the SME 450 of the AP 110determines whether or not to adapt transmit power level of the WTRU 105(step 402). In step 404, the SME 450 transmits a first message(MLME-TPCADAPT.req) to the MLME 455 of the AP 110 requesting TPCinformation if the SME 450 determines in step 402 to adapt the transmitpower level of the WTRU 105. In step 406, the MLME 455 transmits asecond message (MLME-TPCADAPT.cfm) to the SME 450 confirming receipt ofthe first message (MLME-TPCADAPT.req). In step 408, the MLME 455transmits a third message (TPC request frame) to the target WTRU 105requesting TPC information, and the MLME 465 of the target WTRU 105receives the third message (TPC request frame). In step 410, the MLME465 performs one or more physical measurements to determine TPCparameters such as WTRU transmit power level, WTRU receive power level,link margin (i.e., transmit power minus receive power), PSNI, RSSI,RCPI, or the like. The results of the measurements to determine TPCparameters may be forwarded to the SME 470 and stored in the MIB 175 ofthe WTRU 105. In step 412, the MLME 465 of the target WTRU 105 transmitsa fourth signal (TPC report frame) including the requested TPCinformation to the AP 110. In step 414, the MLME 465 transmits a fifthmessage (MLME-TPCREPORT.ind) including the requested TPC information tothe SME 450. The SME 450 may store the requested TPC information in theMIB 160 of the AP 110, such that the TPC information is available toexternal RRM entities. The TPC request is completed in step 416.

FIG. 5 is a flowchart of an exemplary process 500 including method stepsfor transferring TPC information between network entities in accordancewith the present invention.

As shown in FIG. 1A, process 500 is implemented in a wirelesscommunication system 100 including at least one AP 110 and at least WTRU105. As shown in FIG. 1B, the AP 110 includes a first management entity150 and a second management entity 155. Furthermore, as shown in FIG.1B, the WTRU 105 includes a third management entity 165 and a fourthmanagement entity 170.

Referring to FIG. 5, the first management entity 150 in an AP 110determines whether or not to adapt the transmit power level of the WTRU105 (step 505). In step 510, the first management entity 150 transmits afirst message to the second management entity 155 in the AP 110requesting TPC information if the first management entity 150 determinesto adapt the transmit power level of the WTRU 105 in step 505. In step515, the second management entity 155 transmits a second message to thefirst management entity 150 confirming receipt of the first message. Instep 520, the second management entity 155 transmits a third messageincluding a request for TPC information to the WTRU 105. In step 525,the third management entity 165 in the WTRU 105 receives the thirdmessage. In step 530, the third management entity 165 performs one ormore physical measurements to determine TPC parameters. The thirdmanagement entity 165 may transfer the results of the physicalmeasurements to the fourth management entity 170, which in turn maystore the results of the physical measurements in the MIB 175. In step535, the third management entity 165 transmits a fourth messageincluding the requested TPC information to the AP 110. In step 540, thesecond management entity 155 in the AP 110 receives the fourth message.In step 545, the second management entity 155 transmits a fifth messageincluding the requested TPC information to the first management entity.The requested TPC information may then be stored in the MIB 160 of theAP 110.

While this invention has been particularly shown and described withreference to preferred embodiments, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the scope of the invention describedhereinabove.

1. A method of exchanging measurements in wireless communications, themethod comprising: receiving a measurement request, wherein themeasurement request includes a request for a measurement of a parameter;transmitting a measurement report, wherein the measurement reportincludes the requested measurement of the parameter; and storing therequested measurement of the parameter in a management information base(MIB).
 2. The method of claim 1, wherein the measurement report includesan absolute value of the requested measurement.
 3. The method of claim1, wherein the measurement report includes a statistical average of therequested measurement.
 4. The method of claim 1, wherein the measurementreport includes a histogram of values of the parameter over time.
 5. Themethod of claim 1, wherein the parameter includes a signal-to-noiseindicator.
 6. The method of claim 1, wherein the parameter includes areceived channel power indicator (RCPI).
 7. The method of claim 1,wherein the parameter includes a link measurement.
 8. The method ofclaim 1, wherein the parameter includes a clear channel assessment (CCA)busy fraction.
 9. The method of claim 1 wherein the request for themeasurement is a request for a stored measurement of the parameter. 10.The method of claim 1 wherein the request for the measurement is arequest to perform a new measurement of the parameter.
 11. An accesspoint (AP) comprising: a management entity configured to: receive ameasurement request, wherein the measurement request includes a requestfor a measurement of a parameter, transmit a measurement reportcontaining the requested measurement of the parameter, and a managementinformation base (MIB) configured to store the requested measurement ofthe parameter.
 12. The AP of claim 11, wherein the measurement reportincludes an absolute value of the requested measurement.
 13. The AP ofclaim 11, wherein the measurement report includes a statistical averageof the requested measurement.
 14. The AP of claim 11, wherein themeasurement report includes a histogram of values of the parameter overtime.
 15. The AP of claim 11, wherein the parameter includes asignal-to-noise indicator.
 16. The AP of claim 11, wherein the parameterincludes a received channel power indicator (RCPI).
 17. The AP of claim11, wherein the parameter includes a link measurement.
 18. The AP ofclaim 11, wherein the parameter includes a clear channel assessment(CCA) busy fraction.
 19. The AP of claim 11 wherein the request for ameasurement is a request for a stored measurement of a parameter. 20.The AP of claim 11 wherein the request for a measurement is a request toperform a new measurement of a parameter.